1. Field of the Invention
The present invention relates to a scroll compressor, and more particularly, to a back pressure structure of an intermediate pressure of a scroll compressor in which an intermediate pressure space between a main frame and a orbiting scroll is maintained in a constant intermediate pressure state to thereby prevent an abnormal movement of the orbiting scroll, so that leakage of a compressed gas is prevented, and a position of a suction hole on a fixed scroll is freely selected to be formed, thereby facilitating its fabrication.
2. Description of the Background Art
In general, there are three types of compressors, that is, a reciprocating type, a scroll type and a centrifugal type (widely called a turbo type). The scroll type compressor sucks and compresses gas and discharges it by using a rotor like the centrifugal type or a sliding vane type.
The scroll compressor is classified by a low pressure type scroll compressor and a high pressure type scroll compressor depending on the fact that a suction gas is charged inside a casing or a discharge gas is charged therein.
The high pressure type scroll compressor uses a back pressure method of an intermediate pressure in which the gas permeated between the orbiting scroll and the main frame out of a high pressure discharge gas is partially orbited toward a suction chamber so that an intermediate pressure is maintained between the orbiting scroll and the main frame.
FIG. 1 is a vertical-sectional view of a horizontal type scroll compressor of a high pressure type scroll compressor in accordance with a conventional art.
As shown in the drawing, the conventional horizontal type scroll compressor is constructed in that a main frame 2 and a sub-frame 3 are respectively fixed at both sides of a horizontal casing 1 filled with oil at a predetermined height, a drive motor 4 having a stator 4A and a rotor 4B is mounted between the main frame 2 and the sub-frame 3, and a driving shaft 5 is press-fitted by passing through the main frame 2 at the center of the rotor 4B of the drive motor.
A wrap 6a is formed in an involute curve on the upper surface of the main frame 2 so that the orbiting scroll 6 combined eccentrically to the driving shaft 5 is rotatably installed. On the upper surface of the orbiting scroll 6, a fixed scroll 7, where a wrap 7a is formed in an involute curve so as to form a plurality of compressive chambers by being engaged with the wrap 6a of the orbiting scroll 6, is fixedly installed at the main frame 2.
At one side of a plate at margin of the fixed scroll 7 contacted when the orbiting scroll 7 is orbited, a suction pressure space 7c in which a flat plate-type back pressure control valve 8 elastically supported by a coil spring 9 is installed is formed.
A suction hole 7d that is opened and closed when the orbiting scroll 8 is orbited is formed at the side close to the compressive chamber of the suction pressure space 7c of the fixed scroll 7.
At the side of the suction pressure space 7c toward the compressive chamber, there are formed a vent hole 7e for guiding the intermediate pressure gas flown into the suction pressure space 7c through the suction hole 7d to the outermost compressive chamber among the compressive chambers.
Reference numeral 5a denotes a oil passage, 7f denotes a leak resistance stopper, 11 denotes a discharge pipe, 10 denotes a suction pipe, and MS denotes an intermediate pressure space.
The operation of the scroll compressor constructed as described above according to the conventional art will now be explained.
When a power is supplied, the rotor 4B is rotated along with the driving shaft 5 in side the stator 4A by the power, rendering orbiting scroll 6 eccentrically rotated as long as the eccentric distance, and as the orbiting scroll 6 is orbited at a distance as long as the revolving diameter centering around the driving shaft 5, a plurality of compressive chambers are formed between the wraps 6a and 7a of the orbiting scroll 6 and the fixed scroll 7.
As the orbiting scroll 6 is continuously orbited and moved toward the center, the volume of the compressive chambers is reduced, according to which a coolant gas flown therein through the suction pipe 10 is compressed and discharged to the inside of the casing 1 through the discharge port 7b of the fixed scroll 7 in the final compressive chamber.
The discharge gas of high pressure discharged to the inside of the casing 1 flows toward the sub-frame 3 through a coolant passing hole (not shown) formed in the main frame, and thus, the entire casing 1 is highly pressurized, of which a partial gas flows into the intermediate pressure space MS formed between the main frame 2 and the orbiting scroll 6 through a void between the driving shaft 5 and the main frame 2.
The highly pressurized discharge gas flown into the intermediate pressure space MS thrusts the main frame 2 and the orbiting scroll 6 in the opposite directions to each other, resulting in that the orbiting scroll 6 and the fixed scroll 7 are excessively adhered, which causes an increase of a friction loss.
However, in this respect, in case that the pressure of the intermediate pressure space MS goes beyond a set value of a spring elasticity value determined by a spring elasticity determined by the coil spring 9, when the orbiting scroll is rotatably moved, the intermediate pressure gas pushes upward the back pressure control valve 8 and flows to the suction pressure space 7c through the opened suction hole 7d.
The intermediate gas flown to the intermediate pressure space 7c flows to the first compressive chamber through the vent hole 7e to thereby maintain the pressure of the intermediate pressure space MS at an adequate level, thereby preventing an excessive friction loss for the orbiting scroll 6 and the fixed scroll 7.
Thereafter, when the suction hole 7d is closed according as the orbiting scroll 6 is continuously orbited, the back pressure control valve 8 is lowered down by the coil spring 9, thereby blocking the suction hole 7d.
However, as to the back pressure structure of the intermediate pressure of the conventional scroll compressor, since the bottom plane of the back pressure control valve 8 is flatly formed so as to be contacted with the plane where the suction hole 7d of the suction pressure space 7c is formed, the areas pressurized by the discharge gas flown into the suction hole 7d are different to each other according to the opening and closing state of the valve 8.
Thus, a reactivity of the back pressure control valve 8 is delayed, so that the variation of the intermediate pressure is deepened, and thus, the movement of the orbiting scroll 6 becomes unstable, degrading the efficiency of the compressor.
In addition, there is a restriction for the suction hole 7d in the aspect that it must be formed within the orbiting radius of the orbiting scroll 6.